In filtering air, it is desirable that the unfiltered air pass slowly through the filtering material in order to maximize the filtering effect. However, it is also desirable that the air be filtered as quickly as possible in order to minimize the time needed to filter the air in a given room. A solution to these conflicting goals is to provide a large surface area for the filtering material through which the unfiltered air travels.
In order to increase the surface area of the filtering material without unduly adding to the size of the filtering device, multi-sided filtering units or circular filtering units have been devised. In these units, the entire perimeter of the filtering device houses filtering material, thereby maximizing the area of the filtering material in relation to the size of the filtering device.
One such filtering device is described in connection with U.S. Pat. No. 4,749,390 to Burnett et al. In this device, each of the four sides of the filtering device houses one or two frames holding the filtering media. While this device is extremely effective in filtering air, the structure of the filtering device and the containers for the filtering media are somewhat complex to manufacture. Therefore, this device is relatively expensive.
Similarly, with present-day circular filters, the filtering media is housed in a cylindrical container, much like a carburetor air filter. These units also are expensive due to the complexity in constructing the unit to receive replaceable filters. Additionally, the cost of the filter media is relatively high, especially if odor adsorbents are included. The consumer is also given very little choice in filtering materials since the high cost of manufacturing requires high volume production levels of selected products.
Therefore, a need has arisen in the industry for an apparatus and method for filtering air using a multi-sided air filter with a reduced cost of construction.